U.S. patent application number 10/396478 was filed with the patent office on 2003-09-04 for method of connecting two elongated portions of metallic plate, method of manufacturing exhaust pipe of two-passage construction, and exhaust pipe of two-passage construction.
This patent application is currently assigned to KABUSHI KAISHA YUTAKA GIGEN. Invention is credited to Eguchi, Yoshihiko, Hosoda, Fumio, Ishii, Kazuo, Munemura, Takeshi, Sasagase, Takeshi, Sato, Noriyuki, Shirai, Hirokazu, Suzuki, Akihiro, Uegane, Masayuki, Yanagibayashi, Hiroto, Yoshitoshi, Nobuyuki.
Application Number | 20030163918 10/396478 |
Document ID | / |
Family ID | 27341737 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030163918 |
Kind Code |
A1 |
Yoshitoshi, Nobuyuki ; et
al. |
September 4, 2003 |
Method of connecting two elongated portions of metallic plate,
method of manufacturing exhaust pipe of two-passage construction,
and exhaust pipe of two-passage construction
Abstract
In manufacturing an exhaust pipe of two-passage construction, a
metallic plate having a first end and a second end respectively
elongated in a longitudinal direction of the exhaust pipe is
prepared. The metallic plate is bent into a substantially S shape
in cross section. It has a diametrically extending central
partition plate and a substantially semicircular peripheral wall on
each lateral side of said partition plate in such a manner that a
groove of substantially V shape in cross section having a
substantially closed end on a radially inner side and an open end
on a radially outer side is formed at each diametrically outer
portion of the partition plate. A target is provided so as to
elongate along the groove in a manner to extend substantially
radially outward from the closed end. A welding arc is generated
between the target and a welding gun disposed on a side of the open
end such that the substantially closed end and the target are
welded together.
Inventors: |
Yoshitoshi, Nobuyuki;
(Shizuoka-ken, JP) ; Yanagibayashi, Hiroto;
(Shizuoka-ken, JP) ; Shirai, Hirokazu;
(Shizuoka-ken, JP) ; Suzuki, Akihiro;
(Shizuoka-ken, JP) ; Sato, Noriyuki;
(Shizuoka-ken, JP) ; Sasagase, Takeshi;
(Shizuoka-ken, JP) ; Hosoda, Fumio; (Shizuoka-ken,
JP) ; Ishii, Kazuo; (Tochigi-ken, JP) ;
Uegane, Masayuki; (Tochigi-ken, JP) ; Munemura,
Takeshi; (Tochigi-ken, JP) ; Eguchi, Yoshihiko;
(Tochigi-ken, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN & HATTORI, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
KABUSHI KAISHA YUTAKA GIGEN
Hamamatsu-shi
JP
|
Family ID: |
27341737 |
Appl. No.: |
10/396478 |
Filed: |
March 26, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10396478 |
Mar 26, 2003 |
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09742280 |
Dec 22, 2000 |
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6575198 |
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Current U.S.
Class: |
29/890.08 ;
138/115; 138/171; 219/61 |
Current CPC
Class: |
B23K 33/00 20130101;
F01N 2470/06 20130101; B21C 37/0803 20130101; B21C 37/151 20130101;
F01N 2470/10 20130101; B23K 33/008 20130101; F01N 13/08 20130101;
Y10T 29/49398 20150115; F01N 13/14 20130101; F16L 9/18
20130101 |
Class at
Publication: |
29/890.08 ;
138/115; 138/171; 219/61 |
International
Class: |
B21D 051/16 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 1999 |
JP |
366749/1999 |
Apr 10, 2000 |
JP |
107839/2000 |
Jul 6, 2000 |
JP |
204895/2000 |
Claims
What is claimed is:
1. A method of connecting two elongated portions of a metallic
plate, comprising the steps of: longitudinally disposing said two
elongated portions at an angle so as to form a groove of
substantially V shape in cross section having a substantially
closed end and an open end; providing a target elongated along said
groove, said target extending from said substantially closed end
toward said open end; and generating a welding arc between said
target and a welding gun disposed on a side of said open end above
said target such that said substantially closed end of said two
elongated portions and said target are welded together.
2. The method according to claim 1, wherein said target is formed
by bending that end of one of said elongated portions which lies on
said substantially closed end toward said open end.
3. The method according to claim 2, wherein said target lies on an
inner surface of the other of said elongated portions.
4. The method according to claim 1, wherein said target is formed
by an independent target other than said elongated members.
5. A method of manufacturing an exhaust pipe of two-passage
construction, comprising the steps of: preparing a metallic plate
having a first end and a second end respectively elongated in a
longitudinal direction of the exhaust pipe; bending the metallic
plate into a substantially S shape in cross section having a
diametrically extending central partition plate and a substantially
semicircular peripheral wall on each lateral side of said partition
plate in such a manner that a groove of substantially V shape in
cross section having a substantially closed end on a radially inner
side and an open end on a radially outer side is formed at each
diametrically outer portion of said partition plate; providing a
target elongated along said groove in a manner to extend
substantially radially outward from said closed end; and generating
a welding arc between said target and a welding gun disposed on a
side of said open end such that said substantially closed end and
said target are welded together.
6. The method according to claim 5, wherein said target is formed
by bending the first end and the second end, respectively, of said
metallic plate toward the diametrically outer end of said partition
plate.
7. The method according to claim 5, wherein said target is formed
by doubly folding a radially outer portion of said partition plate
substantially into a U shape, a closed end of said U shape facing
radially outward in said groove.
8. The method according to claim 6, wherein said target is formed
by providing an independent member other than said metallic
plate.
9. The method according to claim 5, wherein said target lies on an
inner surface, in said groove, of said partition plate.
10. A method of manufacturing an exhaust pipe of two-passage
construction, comprising the steps of: a) bending two
longitudinally elongated metallic plates respectively into
substantially semicircles with longitudinally elongated sides being
further bent radially inward to thereby form inwardly inclined end
portions; b) assembling the semicircles obtained in step a)
together such that said inclined end portions of one semicircle
face corresponding inclined end portions of the other semicircle to
thereby form a substantially circular semi-product, said
semi-product having on each diametrically opposite sides thereof a
groove of substantially V shape in cross section with a
substantially closed end on a radially inner side and an open end
on a radially outer side; c) interposing a diametrically extending
central partition plate along said grooves in a manner to extend
diametrically outward from said closed ends, whereby a target is
formed by a portion extended beyond each of said closed ends; and
d) generating a welding arc between said target and a welding gun
disposed on a side of said open end such that said substantially
closed end and said target are welded together.
11. An exhaust pipe of two-passage construction comprising: a
central partition plate extending in a diametrical direction and in
a longitudinal direction throughout the exhaust pipe; a
substantially semicircular peripheral wall on each lateral side of
said partition plate so as to extend in the longitudinal direction
of said partition plate, said partition plate and each of said
peripheral walls jointly forming at each of radially outer portions
of said partition plate a groove of substantially V shape in cross
section having a substantially closed end on a radially inner side
and an open end on the radially outer side; and a target elongated
along said groove in a manner to extend substantially radially
outward from said substantially closed end of said groove, said
target being adapted to be integrally welded with the radially
inner side of said groove.
12. The exhaust pipe of two-passage construction according to claim
11, wherein said central partition plate and said semicircular
walls are formed by one metallic plate and wherein said target is
formed by bending each end of said semicircular walls.
13. The exhaust pipe of two-passage construction according to claim
11, wherein said target is formed by doubly folding a diametrically
outer portion of said partition plate substantially into a U shape,
a closed end of said U shape facing radially outward in said
groove.
14. The exhaust pipe of two-passage construction according to claim
11, wherein said target is formed by providing an independent
target member other than said partition plate and said semicircular
wall.
15. The exhaust pipe of two-passage construction according to claim
12, wherein said target lies along an inner surface, in said
groove, of said partition plate.
16. The exhaust pipe of two-passage construction according to claim
11, wherein said central partition plate and said semicircular
walls are formed by independent members and wherein said target is
constituted by extending said central partition plate beyond said
closed diametrically inner end of said groove.
17. An exhaust pipe of two-passage construction comprising: a
central partition plate extending in a diametrical direction and in
a longitudinal direction throughout the exhaust pipe; a
substantially semicircular wall formed on each lateral side of said
partition plate so as to extend in the longitudinal direction of
said partition plate; and a groove of substantially V shape in
cross section formed on each diametrically outer end portion of
said partition plate, said groove having a welded portion between
said partition plate and a diametrically inner end of said groove,
wherein said welded portion lies radially inward of an imaginary
line of an inner circumference of said semicircular wall.
18. The exhaust pipe of two-passage construction according to claim
17, wherein said partition plate has a larger bending rigidity at a
central portion thereof than at both radially outer portions
thereof.
19. The exhaust pipe of two-passage construction according to claim
17, wherein said partition plate and said semicircular walls are
formed by a single piece of metallic plate.
20. The exhaust pipe of two-passage construction according to claim
18, wherein said partition plate has a larger thickness than the
remaining portion of said exhaust pipe.
21. The exhaust pipe of two-passage construction according to claim
18, wherein said partition plate has a plurality of reinforcing
ribs elongated in the diametrical direction of said partition
plate, said reinforcing ribs being disposed at a longitudinal
distance from each other.
22. The exhaust pipe of two-passage construction according to any
one of claims 17 through 21, wherein said groove of substantially V
shape satisfies a condition of j/W<2, wherein j is a depth from
a diametrically outer end of said groove to a connecting portion
and W is a maximum width of said groove.
23. The exhaust pipe of two-passage construction according to any
one of claims 17 through 21, wherein said groove of substantially V
shape satisfies a condition of L/D.gtoreq.0.05, wherein D is an
imaginary inner diameter of the exhaust pipe and L is a distance
from D to a connecting portion.
24. The exhaust pipe of two-passage construction according to any
one of claims 17 through 21, wherein said groove is formed by a
combination of a curved outer portion and a relatively straight
portion which follows said curved portion toward diametrically
inner end of said groove.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates, in general, to a method of
connecting thin metallic plate (or plates) by welding along a
portion in which a single metallic plate is bent to form a joint
portion for welding together or along a joint portion in which two
members meet together. In particular, it relates to a method of
manufacturing an exhaust pipe of two-passage construction to be
used in an exhaust system of an internal combustion engine, as an
example of a product manufactured by the above-described method. It
also relates to an exhaust pipe of two-passage construction
manufactured by the above and other methods, which is free from
stress concentration due to pulsations of exhaust gases.
[0003] 2. Description of Related Art
[0004] As a method of welding two relatively thin metallic plates
for the purpose of manufacturing a product such as an exhaust pipe
of two-passage construction which is suitable for connection to an
exhaust manifold of a multi-cylinder internal combustion engine of
a motor vehicle, there is known the following method in, for
example, Published Unexamined Japanese Patent Application No.
192727/1997 as shown in FIG. 11. Namely, a single piece of metallic
plate having a first end and a second end respectively elongated in
a longitudinal direction of the exhaust pipe is bent substantially
into S shape (i.e., a configuration of an alphabet "S"), as seen in
cross section. The product thus obtained has: a partition plate or
a partition wall "a" which extends in a diametrical direction and
is elongated in a longitudinal direction of the exhaust pipe; and
substantially semicircular peripheral wall portions b, b on each
lateral side of the partition plate (i.e., on a side at a right
angle to the partition plate). In this manner, independent chambers
d, d are formed between the partition plate "a" and the peripheral
walls b, b for passing therethrough the exhaust gases from the
engine. Diametrical end portions, as seen in cross section, of the
first end and the second end of the metallic plate are respectively
bent radially inward to form connecting pieces c, c which lie along
the partition plate "a " in its assembled state. Radially outer
sides of the connecting pieces c and the partition plate "a" are
welded together from a radially out side to thereby form welding
beads e, e. On both longitudinal end portions of this exhaust pipe,
flanges are welded for connecting the exhaust pipe to the engine on
an upstream side thereof as well as to a catalyst converter on a
downstream side thereof.
[0005] The exhaust pipe of two-passage construction thus formed
has, however, the following disadvantages. Namely, a welding bead e
which is formed in the longitudinal direction of the exhaust pipe
is likely to protrude beyond the outer circumferential surface of
the exhaust pipe. It follows that, when the longitudinal end
portion of this welded exhaust pipe is to be inserted into the
flange for fixing it to the exhaust pipe by means of welding, or
when an outer pipe which is used for covering the inner pipe for
the purpose of thermal insulation is swaged (or tapered to a
smaller diameter) to thereby bring the two members into close
contact with each other, the protruded welding bead e is an
obstacle.
[0006] As a solution, the following arrangement may be considered
as shown in FIG. 12A. The exhaust pipe of two-passage construction
in this example is formed into a substantially S shape in cross
section with a single piece of relatively thin metallic plate. It
is made up of: a central partition plate "a" which forms, as seen
in cross section, a diametrical line of the exhaust pipe and which
extends in the longitudinal direction throughout the exhaust pipe;
a substantially semicircular peripheral wall b which is formed on
each lateral side of the central partition plate "a"; and a
connecting piece c' which is formed on each end of the metallic
plate and which is bent so as to partially overlap with the
partition plate "a" in close contact with each other at each
diametrically outer end of the partition plate "a." As a result, on
each diametrically outer end portion of the partition plate "a",
there is provided a groove (or valley) f substantially in the shape
of an alphabet V. This groove f is formed by an arched end of the
thin metallic plate and that arched end of the semicircular
peripheral wall b which transforms (or changes) into the central
partition plate "a." Welding is then made at this groove f by means
of a welding gun (or a welding torch) g by generating an arc
between the welding gun g and a bottom of the groove f in an
attempt to integrally weld the central partition plate "a" and the
peripheral wall b. In welding, however, electric discharging is
likely to take place toward that portion of the mother material
(peripheral wall b) which is closer to the welding gun g as shown
by arrows g1, g1. As a result of this electric discharging, a lump
h of welded metal (welding bead) is likely to be formed as shown in
FIG. 12B in a manner not to reach deep into the groove (or the
overlapped portion). A penetration bead is sometimes formed to
thereby reduce the strength of the mother material. Sometimes, a
penetrating hole i which breaks through the peripheral wall b is
formed as shown in FIG. 12C. If an attempt is made to enlarge the
width of the groove f, the cross section of the exhaust pipe
approaches the shape of a flattened one, resulting in a reduction
in the area of flow of the exhaust gases.
[0007] The exhaust pipe of two-passage construction as disclosed in
the above-described Published Unexamined Japanese Patent
Application No. 192727/1997 has still another disadvantage as
explained hereinbelow. Namely, when the exhaust gases from the
multi-cylinder internal combustion engine pass through a right side
passage (as shown in FIG. 11), the central partition plate "a"
tends to deflect toward the left side by the exhaust pressure as
shown by dotted lines a1. When the exhaust gases pass through the
left side passage d, the central partition plate "a" tends to
deflect toward the right side by the exhaust pressure as shown by
dotted lines a2. As a result, by the pulsation of the exhaust gases
to pass through the two passages d, d, the partition plate "a"
vibrates by alternately bending in opposite directions as shown by
dotted lines a1, a2. This bending takes place with the following
point serving as the point of bending, i.e., each welding portion
between the connecting piece "c" and the partition plate "a" or a
portion which lies on the radially inside thereof. Stresses are
concentrated on these points of bending and fatigue occurs there if
the vibrations continue.
[0008] In view of the above-described points, the present invention
has an object of providing a method of connecting two elongated
portions of a metallic plate by welding, a method of manufacturing
an exhaust pipe of two-passage construction as an example of a
product manufactured by the above-described method, as well as an
exhaust pipe of two-passage construction manufactured by the above
and other methods.
SUMMARY OF THE INVENTION
[0009] In order to attain the above and other objects, according to
one aspect of the present invention, there is provided a method of
connecting two elongated portions of a metallic plate, comprising
the steps of: longitudinally disposing the two elongated portions
at an angle so as to form a groove of substantially V shape in
cross section having a substantially closed end and an open end;
providing a target elongated along the groove, the target extending
from the substantially closed end toward the open end; and
generating a welding arc between the target and a welding gun
disposed on a side of the open end above the target such that the
substantially closed end of the two elongated portions and the
target are welded together.
[0010] Preferably, the target is formed by bending that end of one
of the elongated portions which lies on the substantially closed
end toward the open end. The target may be arranged to lie on an
inner surface of the other of the elongated portions, or may be
formed by an independent target other than the elongated
members.
[0011] According to this method, welding arc is generated in a
manner directed to the target. Therefore, an accurate welding is
possible, and thus even a relatively thin metallic plate can be
welded without giving rise to the problem that the penetrating hole
breaks through the metallic plate.
[0012] According to another aspect of the present invention, there
is provided a method of manufacturing an exhaust pipe of
two-passage construction, comprising the steps of: preparing a
metallic plate having a first end and a second end respectively
elongated in a longitudinal direction of the exhaust pipe; bending
the metallic plate into a substantially S shape in cross section
having a diametrically extending central partition plate and a
substantially semicircular peripheral wall on each lateral side of
the partition plate in such a manner that a groove of substantially
V shape in cross section having a substantially closed end on a
radially inner side and an open end on a radially outer side is
formed at each diametrically outer portion of said partition plate;
providing a target elongated along the groove in a manner to extend
substantially radially outward from the closed end; and generating
a welding arc between the target and a welding gun disposed on a
side of the open end such that the substantially closed end and the
target are welded together.
[0013] Preferably, the target is formed by bending the first end
and the second end, respectively, of the metallic plate toward the
radially outer end of the partition plate. The target may also be
formed by doubly folding a radially outer portion of the partition
plate substantially into a U shape such that a closed end of the U
shape faces radially outward in the groove. The target may also be
formed by providing an independent member other than the metallic
plate. The target may still furthermore be arranged to lie on an
inner surface, in the groove, of the partition plate.
[0014] According to this method, the welding bead can be formed
accurately on the closed end of the groove.
[0015] According to still another aspect of the present invention,
there is provided a method of manufacturing an exhaust pipe of
two-passage construction, comprising the steps of: a) bending two
longitudinally elongated metallic plates respectively into
substantially semicircles with longitudinally elongated sides being
further bent radially inward to thereby form inwardly inclined end
portions; b) assembling the semicircles obtained in step a)
together such that the inclined end portions of one semicircle face
corresponding inclined end portions of the other semicircle to
thereby form a substantially circular semi-product, the
semi-product having on each diametrically opposite sides thereof a
groove of substantially V shape in cross section with a
substantially closed end on a radially inner side and an open end
on a radially outer side; c) interposing a diametrically extending
central partition plate along the grooves in a manner to extend
diametrically outward from each of the closed ends, whereby a
target is formed by a portion extended beyond each of the closed
ends; and d) generating a welding arc between the target and a
welding gun disposed on a side of the open end such that the
substantially closed end and the target are welded together.
[0016] According to the above method, an exhaust pipe of
two-passage construction can be made not by a single piece of
metallic plate but by combining three different pieces of metallic
plate.
[0017] According to still further aspect of the present invention,
there is provided an exhaust pipe of two-passage construction
comprising: a central partition plate extending in a diametrical
direction and in a longitudinal direction throughout the exhaust
pipe; a substantially semicircular peripheral wall on each lateral
side of the partition plate so as to extend in the longitudinal
direction of the partition plate, the partition plate and each of
the peripheral walls jointly forming at each of radially outer
portions of the partition plate a groove of substantially V shape
in cross section having a substantially closed end on a radially
inner side and an open end on the radially outer side; and a target
elongated along the groove in a manner to extend substantially
radially outward from said substantially closed end of the groove,
the target being adapted to be integrally welded with the radially
inner side of the groove.
[0018] Preferably, the central partition plate and the semicircular
walls are formed by one metallic plate and the target is formed by
bending each end of the semicircular walls. The target may be
formed by doubly folding a diametrically outer portion of the
partition plate substantially into a U shape such that a closed end
of the U shape faces radially outward in the groove. The target may
be formed by providing an independent target member other than the
partition plate and the semicircular wall. The target may be
arranged to lie along an inner surface, in the groove, of the
partition plate, or may be constituted by extending the central
partition plate beyond the closed radially inner end of the
groove.
[0019] According to the above-described arrangement, there can be
obtained an exhaust pipe of two-passage construction which is
superior in welding quality by making use of the target.
[0020] According to a still further aspect of the present
invention, there is provided an exhaust pipe of two-passage
construction comprising: a central partition plate extending in a
diametrical direction and in a longitudinal direction throughout
the exhaust pipe; a substantially semicircular wall formed on each
lateral side of the partition plate so as to extend in the
longitudinal direction of the partition plate; a groove of
substantially V shape in cross section formed on each diametrically
outer end portion of the partition plate, the groove having a
welded portion between the partition plate and a radially inner end
of the groove, wherein the welded portion lies radially inward of
an imaginary line of an inner circumference of the semicircular
wall.
[0021] Preferably, the partition plate has a larger bending
rigidity at a central portion thereof than at both radially outer
portions thereof. The partition plate and the semicircular walls
may be formed by a single piece of metallic plate. The central
portion of the partition plate may have a larger thickness that the
remaining portion of the exhaust pipe. The partition plate may also
have a plurality of reinforcing ribs elongated in the diametrical
direction of the partition plate, the reinforcing ribs being
disposed at a longitudinal distance from each other. The groove
preferably satisfies a condition of j/W<2, wherein j is a depth
from a diametrically outer end of the groove to a connecting
portion and W is a maximum width of the groove. Otherwise, the
groove of substantially V shape satisfies a condition of
L/D.gtoreq.0.05, wherein D is an imaginary inner diameter of the
exhaust pipe and L is a distance from D to a connecting
portion.
[0022] According to this arrangement, there can be obtained an
exhaust pipe of two-passage construction which is less subjected to
the stresses due to the pulsations of the exhaust gases. If the
groove is formed to satisfy the above conditions, welding becomes
easy with a particular kind of welding gun.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects and the attendant advantages of
the present invention will become readily apparent by reference to
the following detailed description when considered in conjunction
with the accompanying drawings wherein:
[0024] FIG. 1 is a perspective view of an exhaust pipe of
two-passage construction to which the present invention is
applied;
[0025] FIG. 2A is a sectional view of the exhaust pipe according to
one example of the present invention and FIG. 2B is a sectional
view of a welded portion in a groove;
[0026] FIG. 3 is a sectional view of the exhaust pipe with a
modified example of a target of FIG. 2A;
[0027] FIG. 4 is a sectional view of the exhaust pipe with another
modified example of the target of FIG. 2A;
[0028] FIG. 5A is a sectional view of the exhaust pipe with still
another modified example of the target of FIG. 2A and FIG. 5B is an
enlarged sectional view of a portion to be welded;
[0029] FIG. 6 is a modified example of an exhaust pipe in which the
partition plate is made of a member which is different from the
peripheral walls;
[0030] FIG. 7 is a sectional view of an exhaust pipe in which
stresses of a partition plate are reduced;
[0031] FIG. 8 is a perspective view of an exhaust pipe in which the
partition plate has a reinforced construction;
[0032] FIG. 9 is a modified example of FIG. 8;
[0033] FIG. 10 is a graph showing the relationship between the
stresses ratio of the partition plate and the depth of a
groove;
[0034] FIG. 11 is a sectional view of a conventional exhaust pipe
of two-passage construction; and
[0035] FIGS. 12A through 12C are sectional views of an exhaust pipe
of two-passage construction before improvement of the present
invention has been made, wherein FIG. 12A is a sectional view
showing the occurrence of welding arcs, FIG. 12B is a sectional
view of an incomplete welding beam, and FIG. 12C is a sectional
view showing a partition plate broken by overpenetration of a
welding arc.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0036] First of all, detailed explanation will now be made about
preferred embodiments of the present invention of a method of
connecting two elongated portions of a metallic plate as
exemplified by a method of manufacturing an exhaust pipe of
two-passage construction for use in an exhaust system of an
internal combustion engine.
[0037] FIG. 1 shows an exhaust pipe 1 of two-passage construction
which is manufactured by a method of the present invention. In the
figure, reference numeral 2 denotes an outer pipe which is disposed
on the exhaust pipe 1 with a thermally insulating space
therebetween. The exhaust pipe 1 and the outer pipe 2 constitute an
exhaust pipe assembly 3. One end of the outer pipe 2 is reduced in
diameter so as to come into close contact with an outer periphery
of the exhaust pipe 1. A flange 4 is fitted onto the outer
periphery of the reduced outer pipe 2 for connecting the exhaust
pipe assembly 3 to an exhaust manifold (not illustrated) of a
multi-cylinder internal combustion engine of a motor vehicle. The
other end of the outer pipe 2 has also a flange 5 for further
connection to a catalyst container (not illustrated).
[0038] The exhaust pipe 1 is made up of a single piece of a
relatively thin metallic plate which extends in a longitudinal
direction of the exhaust pipe 1 and has a width with a free end on
each lateral side thereof. The metallic plate whose thickness is
about 0.6 through 1.2 mm, for example, is bent so as to have a
central partition plate or wall 6 which extends in a diametrical
direction and is elongated in a longitudinal direction throughout
the exhaust pipe 1, and two passages 8, 8 each of which is formed
by the partition plate 6 and a pair of peripheral walls 7, 7 which
are substantially semicircular as seen in cross section. As shown
in FIG. 2A, each of the semicircular walls 7, 7 starts bending from
the neighborhood of the upper and lower end portions, as seen in
FIG. 2A, (i.e., diametrically outer end portions) of the partition
plate 6. At each of base or end portions of the peripheral walls 7,
7 (i.e., at those portions of the partition plate 6 where the
partition plate 6 and the peripheral walls 7, 7 meet each other),
there are formed inclined portions 9, 9 and bent portions 10, 10,
respectively. On each lateral free end portions of the metallic
plate (i.e., on starting end portions of the peripheral walls 7,
7), there are formed other inclined portions 12, 12 and bent
portions 11, 11, respectively. The free end portions of the
metallic plate is bent substantially backward to thereby form a
target 13. The term "target" denotes a portion or member which
serves the function of a welding wire or a filler wire in arc
welding. The two inclined portions 9, 12 thus form a substantially
V-shaped valley or groove 14 on each diametrically opposite ends of
the partition plate 6. The V-shaped groove 14 has a closed, or
substantially closed, end on the radially inner side and an open
end on the radially outer side. The angle "A" of the V-shaped
groove 14 is about 40.degree., and the target 13 extends radially
outward from a substantially closed end (i.e., radially inner end
of the groove 14) radially outward along a line which evenly
divides the groove 14 into half.
[0039] A welding gun 15 equipped with a welding electrode or a
plasma electrode is disposed on the side of the open end of the
groove 14 off from (or out of contact with) the target 13 such that
the welding gun points to the target 13. The welding gun 15 is
moved in the longitudinal direction along the target 13 (i.e., in
the longitudinal direction of the exhaust pipe 1) while generating
a welding arc between the target 13 and the welding gun 15. The
target 13 and the portion which lies in the neighborhood of the
target 13 are thus melted together to thereby form welding bead 16
along the bottom of the groove 14 as shown in FIG. 2B. Once the
welding of one diametrically outer side is finished, the welding of
the other groove on the diametrically opposite side is similarly
welded. The target 13 can thus be seen to function as a welding
wire.
[0040] As modified examples of the target 13, the following
arrangement may be employed. Namely, as shown in FIG. 3, instead of
bending the free end portions of the metallic plate substantially
backward as in FIG. 2A, a target 13a is formed by doubly folding a
diametrically outer end portion of the partition plate 6
substantially into a U or V shape such that a closed end of the U
or V shape faces radially outward in the groove. The target 13a is
thus formed so as to extend substantially radially outward from the
closed end on the radially inner side of the groove 14.
[0041] Another modified example is shown in FIG. 4. In this
example, a target 13b is formed by inserting an independent
metallic member (piece) in a clearance at the substantially closed
end of the groove 14. The target 13b is thus formed so as to extend
substantially radially outward from the substantially closed end on
the radially inner side of the groove 14.
[0042] Still further example of the target portion is shown in FIG.
5A. The overall arrangement of the exhaust pipe is substantially
the same as that shown in FIG. 2A, the only difference being that a
target 13c is arranged to lie along the inclined portion 9 toward
the radially outer side. In this example, as shown in FIG. 5B, the
welding gun 15 is arranged to generate a welding arc between the
tip of the gun and the front end portion of the target 13c to
thereby form a welding bead 16'.
[0043] Still another modified example of a target 13d is formed as
a part of the partition plate 6 as shown in FIG. 6. In other words,
each of the diametrically outer ends of the partition plate 6 is
arranged to extend beyond the substantially closed bottom end of
the groove 14, whereby a portion 13c corresponding to a target is
formed in a manner substantially similar to that of the
above-described examples in FIGS. 2A, 3 and 4. The difference in
this example from those given in the above figures is that the
exhaust pipe 1 is formed not by a single piece of metallic plate
but is formed by three pieces. In other words, a semicircular wall
portions 7, 7 are formed in a manner symmetrical to each other with
both ends being further bent radially inward. They are then placed
to face each other such that a substantially closed bottom end is
formed by the diametrically inner sides of the bent ends. A
partition plate 6 is disposed between the inclined portions 9,
12/9, 12 through the substantially closed radially inner side of
the groove 14.
[0044] An explanation has so far been made mainly about the
construction of the target portion. Now, an explanation will be
made about the exhaust pipe in which stress concentration on
diametrically outer welded ends of the partition plate due to
pulsations thereof can be prevented, the problem of pulsations
being encountered in the exhaust pipe described with reference to
FIG. 11.
[0045] The exhaust pipe of two-passage construction according to
the present invention is shown in FIG. 7. The construction is
basically the same as that shown in FIG. 2A or the like except for
the way of connecting the diametrically outer ends of the partition
plate 6 (i.e., the portion at the closed bottom end of each groove
14) and both free ends of the metallic plate (i.e., the radially
inner end of each free end). In other words, the target which is an
essential element in the above-described examples may, or may not,
be employed in this particular example. Therefore, no detailed
explanation will be made about the construction that is
substantially the same as those of the above-described examples, by
attaching the same numerals to the same or similar portions. In
this example, the bottom of the groove 14 may be connected together
by a suitable means, such as by welding, to thereby form a
connecting portion 17, 17.
[0046] The imaginary inner diameter of the exhaust pipe of
two-passage construction is D. The depth of the groove 14, i.e.,
the distance from the line of the imaginary inner diameter D to the
connecting portion 17 is defined to be L. The distance between the
outer portions 10, 11 of the curves at the diametrically outer ends
of the groove 14 are defined to be W. The depth from the
diametrically outer ends of the groove 14 to the connecting portion
17 is defined to be j.
[0047] In this arrangement, when the exhaust gases alternately pass
through the two passages 8, 8, the pulsation occurs to thereby
cause the changes in the pressure in the passages 8, 8. As a
result, due to this pressure difference, the partition plate 6
deflects as shown in imaginary lines 6a, 6b in FIG. 7. Namely, this
deflection is repeated by bending the partition plate 6 from the
high-pressure side toward the low-pressure side with the
neighborhood of the connected portions 16, 16 as points of bending.
As compared with the conventional one as shown in FIG. 11, the
diametrical length of this partition plate 6 thus becomes smaller
in length by an amount of 2 times the amount L which is the
distance between the point of contact of the partition plate 6 and
the peripheral wall 7 and the radially innermost position of
contact. The area of the partition plate 6 of receiving pressure
thus becomes smaller and consequently the total pressure to be
operated onto the partition plate 6 becomes smaller. The bending in
the neighborhood of the connected points of contact becomes smaller
and, further, the wall portions in the groove 14 also allows to
bend to some degree as shown by imaginary lines in FIG. 7. As a
consequence, the bending stresses and stress concentration in the
neighborhood of the connected points 17, 17 are alleviated, with
the result that the durability of the partition plate 6 is
increased.
[0048] By the way, the inclined portions 9, 9 and bent portions 10,
10, which together form the respective grooves 14, 14, shall
preferably be arranged as follows. Namely, the inclined portions 9,
9 are formed into a plane (i.e., having a relatively straight
line), and the bent portions 10, 10 are formed into curved portions
which do not form the continuation of the inclined and straight
portions 9, 9, which is different from continuously formed curved
portions 9a, 12a as shown by imaginary lines in FIG. 7. In this
arrangement, the cross-sectional area of the exhaust-gas flow can
be kept larger.
[0049] Further, as shown in FIG. 8, the central wall 6 may be
formed in a thicker plate than the remaining portion of the exhaust
pipe. According to this arrangement, a higher bending rigidity can
be secured in the central portion of the partition plate 6. The
deflection of the partition plate 6 is thus reduced and the
stresses can accordingly be reduced.
[0050] Alternatively, as shown in FIG. 9, a plurality of
reinforcing ribs 18 may be disposed on the partition plate 6 at a
longitudinal distance from each other. According to this
arrangement, the bending rigidity of the partition plate 6 in the
diametrical direction of the partition plate can be increased. As a
consequence, the deflection of the partition plate is reduced and
the stresses can also be reduced. These reinforcing ribs 18 shall
preferably be formed on the relevant portions of the partition
plate 6 before the exhaust pipe is subjected to the bending
work.
[0051] FIG. 10 is a graph showing the stresses which occur at the
connected points 16, 16 with varying distance L. It can be seen
from this graph that a large depth L can reduce the stresses as
compared with the example in which the distance L is made
substantially zero (as in the conventional example in FIG. 11).
[0052] If, on the other hand, this distance L or j is too large,
the cross-sectional area of the passages 11, 12 becomes small. If
the distance W is too small, economical welding work such as MIG
(Inert Metal-arc Welding) or TIG (Inert-gas Tungsten-arc Welding),
or the like cannot effectively be done from the open end of the
groove. As a solution, the groove in this example is formed such
that each of the connected points 16, 16 lies radially inward of
the imaginary line of an inner circumference of the wall (i.e.,
inside the line of diameter D) and that the groove satisfies a
condition of j/W<2, most preferably, 0.5<j/W<2.
[0053] Otherwise, the depth of the groove 14 shall preferably be
made 5% or more of the imaginary inner diameter D, i.e., is formed
to meet the condition of L/D.gtoreq.0.05. In this arrangement, the
stresses in the neighborhood of the connected portions 17, 17 can
surely be reduced. As a consequence, the thickness of the metallic
plate to be used as the exhaust pipe can be made smaller in
thickness, resulting in a smaller weight of the exhaust pipe.
Therefore, when the engine is started, the exhaust pipe rapidly
rises in temperature and the exhaust gases of high temperature can
be sent to the catalyst converter in a shorter period of time. As
an example of the metallic plate for manufacturing the exhaust
pipe, a stainless steel (defined by JIS, Japanese Industrial
Standard, as SUS 430) was used to meet the condition of
L/D.gtoreq.0.05. Then, it has been found that, as compared with the
one in which L/D is near zero, the stresses in this example was
reduced by 10% or more.
[0054] Suppose that the time in which the inlet portion of the
catalyst converter reaches a catalyst active temperature is "x"
seconds with the plate thickness of "t." Then, the time was found
to be 0.9.times.second with the plate thickness of 0.8t and
0.77.times.second with the plate thickness of 0.6t. As can be seen
from these figures, the catalyst converter can be activated at a
shorter time, resulting in an improvement of the exhaust gas
purifying capacity.
[0055] It is readily apparent that the above-described method of
connecting two elongated portions of a metallic plate, method of
manufacturing an exhaust pipe of two-passage construction, and an
exhaust pipe of two-passage construction meet all of the objects
mentioned above and also has the advantage of wide commercial
utility. It should be understood that the specific form of the
invention hereinabove described is intended to be representative
only, as certain modifications within the scope of these teachings
will be apparent to those skilled in the art.
[0056] Accordingly, reference should be made to the following
claims in determining the full scope of the invention.
* * * * *